The invention resides in a wear protection coating comprising of a plurality of layers including a first layer of a metallic hard material dispose directly on a substrate and additional layers disposed on the first metallic hard material layer including in a periodic repetitive arrangement metallic hard and non-metallic materials.
Such a wear protection layer is known for example from DE AS 29 17 348. This patent publication discloses a compound body comprising a base with one or several hard metal layers of different composition without bonding metals, each having a thickness of 1 to 50 .mu.m. One of the hard material layers with thickness of 0.02 to 0.1 .mu.m (20 to 100 nm) each, wherein the hard material composition of each individual layer is different from the hard material composition of the two adjacent single layers. A preferred embodiment of the wear protection layer resides in a first layer of titanium-carbide disposed on the base on which alternately a multitude of layers of the metallic hard materials titanium carbide, titanium nitrate or titanium carbon nitride on one hand, and, on the other hand, the heteropolar hard materials aluminum oxide or zirconium oxide are disposed. The final outer layer may comprise aluminum oxide with a small nitrogen content.
Another wear protection layer is known from DE 3512986 Al. The various layers of metallic hard material may be combinations of the following metallic hard materials: TiC/TiN; TiC/TiB.sub.2 ; TiN/TiB.sub.2 ; TiB.sub.2 /WC; TiB.sub.2 /Ti(C.sub.1 N); TiB.sub.2 /Ti.sub.1 V)C; TiB.sub.2 /(Ti,W)C; (Ti,V)B.sub.2 //(Ti,V)C; (Ti,Nb)B.sub.2 /(Ti,Nb); VB.sub.2 /TiN; VB.sub.2 /WC; HfB.sub.2 /TaC; ZrB.sub.2 /TaC or ZrB.sub.2 /NbC.
It is important that there is a large number of interfaces in the complete layer structure. This provides for a tension-free tenacious protection layer which has good adherence to the base and is very wear resistant. Such wear protection layers are particularly suitable for the coating of metal cutting tools. The wear protection layer can be formed by cathode sputtering wherein several cathodes of various hard metallic material are used and the substrate (base) is disposed on a rotating plate, moved periodically through the deposit areas of the various cathodes.
EP 0 006 534 A2 disclose a wear protection layer which comprises at least five, but preferably more than ten, individual layers of which at least two have different compositions. The first layer disposed on the substrate consists of a carbide and the final outermost layer consists of a boride or a carbide and the intermediate layers comprise carbides, nitrides, oxides, borides or mixtures thereof. As carbides and nitrides, especially compounds with the elements Hf, Zr, Ta and titanium are proposed which are metallic hard materials. The borides preferably comprise compounds including Hf, Ta, Ti, Zr, and N. As oxides the heteropolar hard metals Al--, Hf--, Zr--, Be-- and titanium-oxide are proposed.
DE 31 52 742 C2 discloses a cutting tool with a multilayer coating. The layers of the coating consist of a nitride or carbide of a metal of the IV. side group of the periodic system (Ti, Zr, Hf) and of a nitride, carbide, boride or silicide of a metal of the VI. (side) group (Cr, MO, W). These compounds include elements of the group of the hard metals. The layers are disposed alternately in relatively large numbers, the thicknesses of the metal compounds of the IV. group being 0.05 to 0.5 .mu.m and the thicknesses of the metal layer of the VI. group being 15 to 40% of the layer thicknesses of the metal compounds of the IV. group. The coating comprises up to 500 individual layers.
It is the object of the present invention to provide a wear protection layer which comprises a plurality of individual layers wherein the mechanical, physical and chemical properties of hard metal materials are combined with those of other hard materials. Furthermore, the wear protection layer should have a very low friction coefficient with regard to ceramic and metallic friction partners and a hardness of over 4000 HVO,05.